We propose a continuing investigation of central neurons responsive to cutaneous cooling, warming, and thermal plus mechanical stimulation. Details of neuronal response characteristics to standardized sequences of thermal stimuli will be compared at successive synaptic levels. Emphasis will be placed on studies of the trigeminal system in primates. Microelectrode techniques will be used to obtain extracellular recordings from single thermoreceptive neurons located in: a) the spinal nucleus of V, b) thalamus, and c) cerebral cortex. Particular emphasis will be placed on the anatomical localization of thermal neurons and their relationship to patterns of mechanoreceptor (somatic) localization.